1. Field of the Invention
The present invention is generally related to the control of an internal combustion engine and, more particularly, to the control of a four cycle engine, wherein the timing of the engine is controlled as a function of the engine RPM and the timing is initially set to be controlled to a pre-selected angle after top dead center (ATDC) position of the piston when the engine is operating at idle speed under certain predetermined conditions.
2. Description of the Prior Art
Many different methods and apparatus are well known to those skilled in the art for controlling the operation of an internal combustion engine. Typically, a control procedure varies the timing of the engine as a predetermined function of a parameter such as engine speed, throttle position, load applied to the engine, etc.
U.S. Pat. No. 4,429,671, which issued to Surace on Feb. 7, 1984, discloses a device for automatically adjusting the rotational speed of an internal combustion engine when it is operating under idle conditions. The device automatically adjusts the spark advance for controlling the idling RPM of an internal combustion engine. It comprises a first sensor means connected by a first connection to the intake duct upstream of the throttle valve. The device also comprises a second connection to the duct downstream of the valve. The second connection is controlled by a solenoid valve that is, in turn, controlled by a second sensor means for determining the engine rotational speed. A third sensor means determines the throttle valve position.
U.S. Pat. No. 4,071,002, which issued to Frahm on Jan. 31, 1978, describes a throttle and ignition advance linkage for an internal combustion engine. A carburetor throttle valve of an internal combustion engine is set in timed relation to a timing control coil by a T-shaped throttle control level which is coupled to an external throttle operator and the timing control lever resiliently coupled to the throttle control lever. The two control levers are pivotally mounted on a common pivot pin secured to the engine block. The T-shaped throttle lever is pivotally mounted at the center of the cross-bar with a pair of throttle control cables that are secured to the opposite ends and to an external throttle control. The stem of the lever projects outwardly toward the carburetor valve input element. A cam member includes a slotted and clamp screw connection to one side of the stem to permit adjustment of the cam member along the length of the stem.
U.S. Pat. No. 4,267,810, which issued to Wesemeyer et al on May 19, 1981, discloses a control system for control of repetitive events such as ignition and fuel injection in internal combustion engines. In order to simplify the crankshaft rotation sensor device which provides the computer of a control system with angular speed and position information for ignition and/or fuel injection timing, a signal generated by one pickup for every two engine cylinders from a single reference mark on the crankshaft is formed into a signal pulse which is used to trigger the counting of clock pulses from a clock into a counter. These are then periodically transferred to a computer as a numerical signal which represents the required information. In a first mode, the counts are transferred every other period between pulses and the counter counts in the cycle periods between the pulses in which the counter is not transferring to the computer. In a second mode, the counter counts every cycle between pulses and the counts are transferred during every pulse itself. There is also described in this patent a system which includes additional circuitry by which below a certain speed of the engine the system operates in the first mode and above that speed operates in the second mode.
U.S. Pat. No. 5,107,815, which issued to Van Duyne on Apr. 28, 1992, describes a variable air/fuel engine control system with closed-loop control around a maximum efficiency and combination of otto-diesel throttling. The system is intended to control a spark ignition engine to maximize fuel efficiency over its entire range of operating conditions. The system includes apparatus for controlling the amount of fuel delivered to the engine and apparatus for measuring the internal cylinder pressure in at least one cylinder of the engine. Apparatus is provided for estimating the air mass entering the engine and computing apparatus calculates the engine efficiency from the amount of fuel delivered, internal cylinder pressure, and the estimated air mass entering the engine. In one embodiment, efficiency is measured by calculation of the approximate indicated specific fuel consumption. Apparatus is provided for varying the amount of fuel delivered to the engine to maximize the indicated specific fuel consumption over the entire range of operating conditions of the engine. In this embodiment, apparatus is provided which is responsive to a desired engine power output beyond wide open throttle plate and apparatus is provided for delivering a greater quantity of fuel beyond the wide open throttle plate position maximum efficiency point.
U.S. Pat. 5,608,632, which issued to White on Mar. 4, 1997, describes a self contained sequential throttle by injection engine control system. The system is configured to be attached to the intake port or intake manifold of a reciprocating engine. The system can be designed to allow installation as original equipment or as a retrofit unit. In either case, the system provides the engine with a dual ignition and electronically controlled fuel-injection. The system includes a master control unit that utilizes a firmware operating microprocessor. The control unit is connected to a plurality of sensors that sense critical system parameters that determine the engine settings. All systems parameters are user controlled by three system command switches that are located on a control display unit. The display unit is attached to the control unit by an electrical cable and is positioned on the vehicle to provide easy accessibility.
U.S. Pat. No. 4,580,221, which issued to Isobe et al on Apr. 1, 1986, discloses a method and device for internal combustion engine condition sensing and fuel injection control. Engine condition signals are read out from sensors for detecting conditions of the engine with selected sensor outputs read out in synchronism with rotation of the engine at a predetermined crank angle empirically corresponding to a low engine load and resulting high battery voltage. The predetermined crank angle is within at least 20 crank angle degrees of bottom dead center.
The above patents are hereby explicitly incorporated herein.
An operator who is controlling an internal combustion engine, such as the engine of an outboard motor, typically moves a throttle plate of the engine manually by adjusting a throttle handle to select engine speed. Using any one of many different known throttle controls, such as a tiller handle, an operator can continually move an adjustment device by hand and thereby, through a mechanical linkage, affect the position of a throttle plate located within an air intake assembly of the engine. By opening the throttle, engine speed is increased, and by closing the throttle, engine speed is decreased. In other words, the operator controls the speed of the engine by controlling the air flowing through the engine's intake manifold to its cylinders. When an operator suddenly changes engine speed from a first speed to a faster second speed, this results in two reactions in most internal combustion engines. First, the throttle valve is moved to a more open position. Secondly, and generally simultaneously, a quantity of fuel is injected by a fuel pump into the air stream passing from the air intake manifold to the cylinders of the engines. These two occurrences allow the engine to rapidly respond to the operator's manual request for increased speed.
If, after increasing the speed of an engine, the operator then suddenly decreases the speed, the engine may react in a manner that is not intended. For example, an increase in speed followed by a sudden decrease in speed can result in too much fuel passing into the cylinders. As described above, the initial increase in speed results in an injection of fuel into the air stream by a fuel pump. If the speed is then suddenly reduced before that injected fuel is consumed, the cylinders of the engine will experience a condition wherein a higher than normal quantity of fuel flows into the cylinders is accompanied by a lower than normal quantity of air. This condition could result in stalling.
In order to avoid the situation described immediately above, many throttle controls are provided with a dashpot which ameliorates the action by the operator described above. In other words, when the operator attempts to suddenly open the throttle and then quickly close the throttle, the dashpot mechanically delays the response by the throttle. In other words, the throttle plate closes in response to the operator's control, but in a manner slower than the actual manual change in the control device, such as the tiller handle. The dashpot moderates the movement of the throttle plate so that it does not rapidly close and deprive the cylinders of the required air to burn the fuel that had been injected as a result of the sudden increase in speed caused by the operator. This delayed closing of the throttle plate allows the excess fuel to be burned because the speed of the engine is decreased more slowly than requested by the operator.
Many different types of dashpots are well known to those skilled in the art. However, the inclusion of the dashpot on an internal combustion engine adds cost and complexity. It would therefore be significantly beneficial if a means could be provided to prevent the adverse results described above, when an operator suddenly increases and subsequently quickly decreases engine speed, but without the need for the additional cost and complexity associated with a provision of a dashpot.